[Amps] Initial RF testing of 4CX1000A amplifier

[Peter Voelpel]

OK, understood, but I never saw that in commercial tetrode amplifiers.

The anode to screen voltage will be lower with screen voltage supplied.

I always bias to cut off with grid bias and protect grids and sockets with
surge arrestors by Epson and VDR resistors.

73
Peter

-----Original Message-----
From: Ian White [mailto:ian at ifwtech.co.uk] 
Sent: Mittwoch, 6. November 2013 20:22
To: 'Peter Voelpel'
Subject: RE: [Amps] Initial RF testing of 4CX1000A amplifier

>
>
>What is the reason to have the screen unconnected from its voltage or
>switched?
>
>73
>Peter
>

Amateur amplifiers spend most of their operating time in the RX or 'warm
standby' condition, so there are two reasons for switching the screen to
ground (cathode):

1. HV arcs can occur at any time, and grounding the screen grid provides
maximum protection for both the screen grid and the bypass capacitor
(the socket may be even more expensive than the tube itself). 

2. The shunt stabilizer can be switched into a low-current standby
condition to reduce unnecessary heat dissipation.

Relay switching is simple and reliable, but other options are possible.
K2VCO has configured the Tetrode Boards to use grid-block keying for
QSK, and only switches the screen to ground when the amp is truly in
'standby'.


73 from Ian GM3SEK